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DiagonalRedLine

Model Output Discussion - The Run In To Christmas

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At last!

Good consensus building for what we can expect to see develop over Christmas and into the New Year across the output.

I fully expect the best ECM we have seen for some time in terms of cold being modeled this evening.

 

There is still potential for things to go wrong but the output has very much moved in the right direction through today though GFS ensembles are a little slow to pick out the detail of how shortwave energy will interact with the trough but that is to be expected. Confidence is increased because the higher res of the operational runs is important for detail.

 

We have two areas of shortwave energy to watch just after Christmas, one to the NW and one to the W/SW, timing is important though not actually crucial so long as the closed low to our SW does not push NE and only spits off shortwave energy as it disrupts to our SW.

 

See the following GFS chart with shortwave energy NW and W/SW of the UK.

 

 

gfsnh-0-168.png?12

 

These shortwaves, often the demise of a cold spell are actually just what is needed as the initial trough is too shallow and weak to displace the spoiler Azores high and back the ridge West and thus amplify the pattern enough to bring in the colder polar air.

 

Here they have merged to form low pressure over the UK which will then phase with the main trough to our NE. This period will likely be wet and windy and not cold bu it should also be brief.

 

gfsnh-0-180.png?12

 

 

Now the low moves East and merges with the main trough displacing the Azores high to the South and ridge to the West and amplifying the pattern, dragging in much colder air from the N/NE

 

gfsnh-0-228.png?12

 

Why post just one run and detail the synoptic?

Because this is very much the typical pattern being set up and what the consensus is being built around.

The details will vary but if the models are right about how they are handling the shortwave energy then cold is guaranteed from this pattern.

 

Currently the ensembles want to move the PV back West in the later output and are reluctant to build high pressure over Greenland, in stead offering a 4/5 day cold snap before the Atlantic pushes back in, but this is very much against the background signals so if things turn out along the lines of the above which is currently looking good then we can expect large and rapid upgrades to the severity and longevity of any cold into the New year.

 

If ECM goes the same way this evening and there is a firming up tomorrow I would happily forecast a cold spell in the run to New Year with many areas likely seeing snow.

No more wobbles please! :cold:  :cold:  :cold:  :help:

Edited by Mucka
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Guys I want to be excited but we all know it won't turn out like that these low pressure systems can disapear in an instance as we have seen many times before, and we also need the shortwaves to play ball there are just too many variables and things that can go wrong at 8 days away it always seems that time frame that show this sort of eye candy only to be downgraded as we enter the reliable timeframe, But our luck has to change sometime right.

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If the GFS (p) verifies as shown for the 27th, what areas would be affected by snow? Would the snow be a northern/Midlands event, or would the south get in on the action?

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hi

 

As I understand it...it is when a LP system in situ is squeezed and some of the energy is forced out of the LP:

 

attachicon.gifgfs-0-138 (1).png attachicon.gifgfs-0-150.png attachicon.gifgfs-0-162.png

 

In this instance the original LP remains in situ and the daughter low is ejected NE into the jet.

 

Not sure it is a Met Technical term though!!

Think we invent our language to describe the models on here :)

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If the GFS (p) verifies as shown for the 27th, what areas would be affected by snow? Would the snow be a northern/Midlands event, or would the south get in on the action?

 

Pretty well everyone IMHO. The gales would be awful on North Sea coasts too.

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Please ECM don't let the side down.  So far the models that go out past T144hrs eject the shortwave and this separates from the parent low.

 

This is now the trigger to accelerate the output towards a colder outcome, the further south this shortwave is ejected the better but overall tonights outputs are a step up for cold.

 

We need the ECM operational run to move towards its ensemble cluster and stop this obsession with a west based negative NAO.

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If the GFS (p) verifies as shown for the 27th, what areas would be affected by snow? Would the snow be a northern/Midlands event, or would the south get in on the action?

 

Let's put it this way, it'd probably make the Channel Four news headlines anyway eh John.  :laugh:

 

jonsnow1.jpg

 

Jesting aside, D8 yet alone inside D2 timescales are hard to predict when it comes to SNOW probabilities. Watch this space though, post Christmas is where things are hotting up for coldies, especially for the Midlands Northwards.  :friends:

Edited by gottolovethisweather
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When's the next ecm run folks

Can't believe the last 24-48 hours

Great fun and Great reading

Keep it going folks

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I don't buy this low pressure over Scotland. It just pops up out of absolutely nowhere! No way could it so quickly get so strong? Surely?

 

 

output_UZBtg6.gif

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When's the next ecm run folks

Can't believe the last 24-48 hours

Great fun and Great reading

Keep it going folks

 

Even better reading when these monumental (!) charts (well a bit of lowland snow a plenty) come to fruition consistently within the reliable. All the current hype is focussed on charts beyond Christmas Day, let us NOT forget. I am also not saying things won't pan out as predicted either, simply take it steady guys n gals IF you are looking at things in your own back yard for example at such a range.

Edited by gottolovethisweather

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If the GFS (p) verifies as shown for the 27th, what areas would be affected by snow? Would the snow be a northern/Midlands event, or would the south get in on the action?

 

Did they not tell you, John Snow??

 

Winter Is Coming!!

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ECM out to 120 hrs and wins the most tiny areas of high pressure award. :laugh:

 

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I don't buy this low pressure over Scotland. It just pops up out of absolutely nowhere! No way could it so quickly get so strong? Surely?

 

 

output_UZBtg6.gif

That's why it is known as rapid cyclogenesis. At least a pressure drop of 24mb in 24hrs to qualify.

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I don't buy this low pressure over Scotland. It just pops up out of absolutely nowhere! No way could it so quickly get so strong? Surely?

 

 

output_UZBtg6.gif

It could of course develope earlier and run much further south ,or get pushed further north especially if the azores high flares up ,at this range very interesting but very early days ,hope though its a white one for all with a good undercut ,cheers .

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Too early to judge the ECMWF, but at 144hrs the ridge to the southwest of the UK is a little stronger and there is no evident split of the Atlantic low.

 

ECM1-144.GIF

Edited by Matty M

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ECM on Christmas Day produces yet another dry and sunny signal for most parts akin to the UKMO, but with an additional interesting feature for the SE. Away from there and presumably into Boxing Day it looks a cool and crisp setup, plenty of walks might be taking place in the countryside if this continues. Mid-run so far so I'll let others comment on the deeper FI picture, please be nice ECM, stay on trend. 

Edited by gottolovethisweather
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Too early to judge the ECMWF, but at 144hrs the ridge to the southwest of the UK is a little stronger and there is no evident split of the Atlantic low.

 

ECM1-144.GIF

man am not liking the look of the ecm at the moment!! No seperation of the shortwave! !

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I'll be honest here, I've been looking but not really noting much of the GFS output; it's just been too volatile. Good for fun and games, but past D7 I'm just taking it with a big pinch of salt. The EC is the model I've been looking at more often than not; and in particular the 12z.

and at least at D6, there is some consistency with yesterday's (first pic today's 12z EC at D6, second pic yesterday's 12z for D7 - same date)

ECH101-144.GIF?19-0

ECH101-168.GIF?12

Good general consistency, with a stronger Greenland height profile, and lesser +ve Europe pressure anomaly; good run up to D6 so far I'd say

on that note- some snow shrs for NE Scotland on the day itself; and probably strong gusts and rain/sleet across eastern parts due to the shortwave ECU1-144.GIF?19-0

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Am I right in thinking that in the previous chart, the low pressure rapid development would (might) come about because of the unusually high temperatures shown off the coast of Spain? So if the warmth turns out to be less strong, the "weather bomb" will be less explosive?

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ECH1-168.GIF?19-0

 

Danger Will Robinson, danger!

 

ECM trying desperately to develop the one pattern that could ruin things by timing the shortwave development to allow them to merge - we would be hugely unlucky for that to happen. 

I predict this will be yet again among the very mildest of runs within its ensembles from 168/192.

ECM the Christmas Scrooge but at least it keeps expectations lower (mine anyway) until tomorrow.

I think we will have a very good idea by tomorrow evening which way this going.

 

JMA not perfect but going much more to plan in general terms.

 

JN192-21.GIF?19-12

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ECM says no, with a very west based neg NAO and a screaming SW flow over Britain by Dec 27

 

ECM1-192.GIF

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ECM1-168.GIF?19-0

messy west based nao and azores ridge ecm really does change like the weather.

 

but wait says the ecm lets try again in the mean time we all get blow torched but lows and highs to our south fight it out.

but still could produce in the longer term....

ECM1-192.GIF?19-0

and then its back to square one like we recently been getting.

flattened by the sumo vortex

ECM1-216.GIF?19-0

 

i did say recently that its possible it could miss and go into europe classic close no cigar and in a worse situation than we are now awful ecm.

ECM1-240.GIF?19-0

Edited by emotional rollercoaster

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Well at 192 hours ecm seems light years from the other models???Pressure to the south is higher but how can there be so much distance ie output????

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